Eclipse showing "Maven Configuration Problem: Unknown"

This seems like a bug in eclipse: https://bugs.eclipse.org/bugs/show_bug.cgi?id=547340

You can fix this by temporary downgrading the maven jar plugin version to 3.1.1 from 3.1.2. Add this to the properties section:

<maven-jar-plugin.version>3.1.1</maven-jar-plugin.version>

So your pom will look like this:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.5.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.in28minutes.springboot.rest.example</groupId>
<artifactId>spring-boot-2-jpa-with-hibernate-and-h2</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring-boot-2-jpa-with-hibernate-and-h2</name>
<description>Demo project for Spring Boot</description>

<properties>
    <java.version>11</java.version>
    <maven-jar-plugin.version>3.1.1</maven-jar-plugin.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>
</project>

Update: A fix has been released. Click Help > Check for updates in Eclipse/STS and install the newest m2e connector.

Step 1:

Downgrade to <maven-jar-plugin.version>3.1.1</maven-jar-plugin.version>

<properties>
    <java.version>X</java.version>
    <maven-jar-plugin.version>3.1.1</maven-jar-plugin.version>
</properties>

Step 2 Update Project

• Right Click on your Project
• Go to Maven
• Click on Update Project
• Clean and Re-Run your Application

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